The present disclosure relates generally to a method of metallurgically bonding an article and an article suitable therefor, and particularly to a surface condition at the article for improving the metallurgical bond.
Vehicle fabrication and assembly may involve a number of metallurgical bonds, such as welds for example, that may be time consuming to create and may require special considerations depending on the materials being bonded. The welding of galvanized parts, or galvanized to aluminum parts, may offer a challenge to the weld practitioner since zinc vapor from the coated steel, and magnesium vapor from magnesium-bearing aluminum alloys, is released at the weld site due to the high vapor pressures or low melting points of the respective materials. As a result, the entrapped vapors may introduce contaminants and/or voids within the solidified weld nugget.
Also of consideration to the weld practitioner may be the thickness of the parts being metallurgically bonded. For example, ultra-thin gage steel, having a thickness on the order of about 0.7 millimeters for example, may be difficult to resistance weld due to the large heat loss at the faying surface to the copper electrodes. The heat build-up at the electrodes tends to cause electrode material softening and facilitates the inter-diffusion between the electrode material and the zinc-rich coating on a galvanized steel surface, which in turn may accelerate electrode wear. As the electrode wears and the cap face flattens, the current density at the electrode-to-sheet interface decreases, resulting in a decrease in weld nugget size in the absence of compensating adjustments. One compensating adjustment may be to dress the electrode face as the electrode starts to wear, which may be time consuming and may be disruptive to high volume production processes.
Another consideration to the weld practitioner may be the use of hydroformed parts, which tend to have thin shells and may experience weld distortion and cracking at the weld site due to the high electrode force and the high weld temperatures required to produce a satisfactory weld.
Accordingly, there is a need in the art of metallurgical bonding methods and arrangements that overcome these drawbacks.